Virtual humans with accurately modelled bones, muscles and nerves could help surgeons predict the effects of operations, according to biomechanics researcher Scott Delp from Stanford University in California, US. Delp presented details of computerised humans created at his lab at the annual Experimental Biology meeting in San Francisco, US, this week.

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“We build computational models of human systems to try and mirror natural movement,” Delp told New Scientist. The models are made by drawing on a wide range of scientific sources on the form and function of the human body. “Medical images are a good source of the body’s form. But the physiology, the function, is more challenging,” he adds.

To make the models as realistic as possible, Delp’s group recorded the forces produced by specific human muscles during different exercises, performed by test subjects. They also took data from experiments carried out by other researchers, including investigations into the way nerves communicate and coordinate with muscles.

“The models integrate a whole set of different pieces of experimental data,” Delp says. “And they can be used as a tool to ask and try to answer a lot of new questions.”

Before and after

The latest virtual humans developed at Delp’s lab are personalised to match real people – his group has created models of children with cerebral palsy whose movements are affected by their illness.

The childhood brain damage that causes cerebral palsy affects muscle control, leading to abnormal muscle development and problems with walking and other movement. Surgery can rearrange bones and muscles to make walking easier, but it is difficult to predict the outcome of each surgical procedure with accuracy.

“Using medical scans we can tweak the model to the individual subject before they have surgery,” Delp explains. “We look at how the children are able to move afterwards and compare that with what we thought would happen – that way we can see what we got wrong and make improvements.”

The models could one day make it possible for surgeon to predict of how effective different surgical procedures will be, Delp says.

“The advantages of a virtual model are huge,” agrees Tim Marler, a computer graphics researcher from the University of Iowa, US, who presented details of his own virtual human, named “Santos”, at the same conference. Marler’s project combines anatomical and physiological data to create a virtual human capable of testing the ergonomics of industrial and military equipment.

Crashed helicopter

“We have modelled all of the primary muscles throughout the body – the way they wrap around bones – and are developing a way of modelling muscle fatigue for the complete body in real time,” Marler says. “With respect to physiology, we are able to predict energy consumption, heart rate, strain index, body temperature, oxygen uptake, and breathing rate.”

This means Santos has built-in limits on strength and stamina that affect its movements and behaviour. Unlike most 3D computer characters, Santos will not always move the same way but will respond to fatigue or to being loaded down with a heavy pack, for example.

“Simulations can be used to solve real-world problems, such as how to escape from a crashed helicopter or how to exit through the emergency hatch of a military vehicle,” Marler says. “Real-world tests are expensive and time intensive but we will be able to place Santos in a vehicle and answer questions about how comfortable a seat is, or how difficult is it to pull a lever, or reach a dial.”

US engineering company Caterpillar has invested money in the Santos project, which it hopes will reduce the costs of designing expensive mining machinery. The US Army Soldier Systems Center, also known as Natick, plans to enlist Santos’s help too, according to Marler. “Natick wants to understand the effects of new armour designs on motion and the completion of various tasks, such as running, diving to the ground, and aiming,” he says.